This invention relates to a radio frequency (RF) coudler and the invention relates particularly, though not exclusively, to an RF coupler for transferring RF power between a first circuit on a rotary shaft and a second circuit relative to which the shaft can rotate.
The invention also relates to a tunable notch filter.
International patent application no. PCT/GB91/00328 discloses an apparatus for measuring dynamic torque in a rotatable shaft. The apparatus comprises a surface acoustic wave (SAW) transducer mounted on the shaft, and requires coupling means for the efficient transfer of RF power between the transducer and processing circuitry which does not rotate with the shaft.